What is Technical SEO? The basics for website audits

Is your website built to respond to the needs of your website visitors, and the search engines or LLMs they use? 

This is the question that a technical SEO audit effectively asks of your website. The technical aspects and components of your website will determine how it works, and considering a well-functioning website is a key driver of organic traffic, leads, and revenue for your business, we’re guessing you’d like your website to be a smooth operator.

As your website exists in a shifting space, the only way to ensure it can ride out any bumps in the road, of which there are many (broken links! rogue duplicate content! algorithm updates!), is to conduct regular audits of its technical performance. 

It may not feel as related to your customer experience as, say, your brand marketing, but your website’s infrastructure — the databases, servers, and storage — has as much of an impact on your ability to acquire and convert leads as your website design.

A high-performing website is a technically optimised one. So, if you need your website to work harder in the digital marketing department, a technical SEO website audit is the best place to start. 

As the Development Director here at Mud, I regularly conduct audits as part of our process of continuously reviewing and optimising the performance of websites we’ve built for our clients. Not to mention diagnosing issues to tackle in the design and development of new website projects, too.

In this article, I’ll introduce you to technical SEO and the role it plays in meeting the criteria demanded by the likes of Google and ChatGPT. Then we’ll get into the basics of web auditing and how to go about identifying and rectifying the issues that may be affecting your site’s performance when it comes to search.

What is Technical SEO?

Technical SEO refers to the optimisation of the technical foundations of your website in order to rank better in search engines and AI search. 

By making your website easier to crawl, understand, and index, you increase the chances of it ranking better on Google and being mentioned and/or cited by the likes of ChatGPT, Claude, and Gemini.

The aim of technical SEO (and all SEO) is to make it more likely for users to be able to find and click on your website and content. 

How well your site performs against the competition comes down to three things: the quality of your content (on-page SEO), external signals like links, mentions, and reviews (off-page SEO), and the technical elements that make up your site's infrastructure — that's technical SEO.

💡Don't miss our guide to building a website that ranks in 2026

What is a Technical SEO audit?

A technical SEO audit is a systematic evaluation of how well your website's technical foundations support both search engines and the people using your site.

What you end up with is a prioritised list: the issues holding your site back, graded by how much damage they're doing, and a clear sense of what to tackle first. Some of those fixes will be undertaken by a developer, some by your content team, and some come down to hosting or CMS configuration. An audit is usually the start of a conversation rather than the end of one.

Certain moments make an audit nigh-on essential. A site migration or replatform, a redesign, an unexplained drop in traffic or visibility, expanding into new markets or languages, or taking on a website someone else built and you're not confident in.

Outside of those, a technical SEO audit isn't a one-off task to be shelved once completed. Websites don't sit still: content teams publish, plugins and CMS versions (should be) update(d), marketing adds integrations, redirects pile up. 

All that is to say: things can break for seemingly no reason. Our recommendation is to always have an eye on SEO performance using tools like Ahrefs, and to run a full audit every quarter.

💡 Further reading: Full Technical SEO Checklist for 2026
 

What Does a Technical SEO Audit Cover?

What are all these technical elements that we're talking about? Let's break it down, and discuss the specific aspects of your website you'd be focusing on as part of an audit.

Crawling and Indexing

Crawling is the process of a bot loading the URLs on your website and analysing them for content and issues. It typically starts from a single point — a sitemap or a home page — and follows links to whatever else it can find.

Indexing is what happens next: how a search engine stores that content so users can find it. To be added to an index, a page has to allow indexing in the first place. Mistakes here are the most expensive mistakes in technical SEO, because getting them wrong doesn't dent your rankings; it removes you from the results entirely. We've seen entire sites disappear from Google because a noindex tag survived the move from staging to live.

Most websites run on a CMS with a handful of templates producing thousands of pages, and even a small number of templates can throw up significant variation in how those pages behave. A crawl tool surfaces what you'd never find by clicking around: broken links, oversized images, slow-loading pages, orphaned content, inaccessible URLs. Fix those, and you're improving how visitors perceive your brand as much as how search engines assess it.

Rendering: What the Bots See

Here's the one that catches people out. There's a difference between the HTML your server sends and the page a visitor eventually sees, and if your content is assembled in the browser by JavaScript, that gap matters enormously.

Google will render JavaScript, though it costs them time and resources, and it doesn't always go to plan. Most AI crawlers won't render it at all. So a page can be perfectly crawlable, perfectly indexable, and still be a blank room to ChatGPT, Claude, or Gemini — because everything of substance arrives after the initial response.

The check is simple enough: view the raw source of your key pages, or fetch them without JavaScript enabled, and see whether your actual content is in there. If it isn't, you've found something worth acting on. It's one of the reasons we build on server-rendered templates rather than shipping the work to the browser and hoping for the best.

AI Crawler Access

Crawlability is no longer just a Google thing. If you want to be cited in AI-generated answers, the platforms doing the citing (ChatGPT, etc.) need to be able to reach your content. And you certainly don't want to lock them out.

Your robots.txt file may be blocking GPTBot, ClaudeBot, PerplexityBot, Google-Extended or CCBot, either because someone decided to or because the setting arrived with a plugin. Your firewall or bot protection may be blocking them at the edge, before robots.txt gets a look in. Some CDN and security providers now block AI crawlers by default, which means plenty of sites are excluded without anyone ever choosing to be.

To be clear: blocking AI crawlers is a perfectly legitimate decision. Some businesses have good reasons for it. But it should be a decision, not an accident, and an audit is where you find out which one you've got. This all sits within Generative Engine Optimisation (GEO), which we've covered in detail.

Site Architecture and Internal Linking

How your content is organised affects how well it performs in search. Think neat, tidy, and logical: intuitive navigation that carries a user (and a crawler) smoothly to your key sections, whether that's product pages, services, or the journal.

Your URL structure does quiet work here too. A URL of services/legal/wills tells both a person and a machine exactly where they've landed and what sits above it. A URL of page-247 tells them nothing at all.

Internal linking is the other half of it, and it's the lever most teams can pull without going anywhere near a developer. The pages you link to most often are the pages you're signalling matter most. Orphan pages — content that nothing else on your site links to — are a sign of neglect, and they're treated accordingly.

Remember that users don't always arrive at your home page. They can land deep inside your site from a search result or a shared link, so a clear indication of where they are and an obvious route to related content are crucial to them having a decent experience.

Redirects and URL Changes

Every site accumulates redirects. Pages get renamed, sections get restructured, a migration happens, and a thousand URLs change at once. Handled properly, redirects preserve the authority those old pages built up. Handled badly, they leak it.

An audit looks for chains (a URL pointing to a URL pointing to another URL), loops, redirects to irrelevant pages or a blanket redirect of everything to the home page, and old URLs still being linked to internally. If you've migrated or redesigned and your traffic never quite recovered, this is usually where the body is buried.

Page Speed and Performance

How quickly your content loads across devices and networks is a core quality indicator, and Google measures it through three Core Web Vitals: Largest Contentful Paint (how long the main content takes to appear), Interaction to Next Paint (how quickly the page responds when someone actually does something), and Cumulative Layout Shift (whether things jump around while loading).

Too slow, and the experience degrades in ways that go well beyond impatience. Elements render out of order, layouts shift under the cursor, and accessibility suffers. For most users, the frustration ends in abandonment — bad news for your acquisition targets — and because Core Web Vitals feed the algorithm, it costs you in the rankings too.

One thing worth understanding: there are two kinds of speed data, and they often disagree. Lab data comes from a simulated test on a synthetic connection, which is what tools like PageSpeed Insights give you instantly. Field data comes from real visitors on real devices, which is what Google actually uses and what you'll see in Search Console. A perfect lab score alongside failing field data usually means your real audience is on slower connections or older phones than your test assumed.

Mobile-Friendliness

Mobile-first indexing is simply how Google works now — your mobile site is your site as far as they're concerned. That settles the old argument about which experience matters more, and moves the question on to what actually breaks.

Content parity is the big one. If something appears on desktop but not mobile — a tab that collapses away, a section hidden behind a breakpoint, a table that doesn't survive the narrow view — then as far as Google is concerned, it may as well not exist. Beyond that: tap targets big enough to hit with a thumb, no intrusive interstitials ambushing people the moment they land, and media sized sensibly for a phone rather than shipped down at desktop dimensions and scaled.

Lazy loading helps here, loading what's on screen first and fetching the rest as the user scrolls. Faster initial load, less bandwidth burned, better experience — no need to download a hero image sized for a 27-inch monitor onto a handset on patchy 4G.

Security

Search engines want to know they're sending people somewhere safe, so an audit checks that HTTPS is properly implemented and your SSL certificate is valid. SSL encrypts data moving between browser and server, and it's now expected across entire sites regardless of whether anything sensitive changes hands.

The renewal side of this is changing, and it's worth knowing about. Certificate lifespans are being cut industry-wide: from March 2026, newly issued certificates last a maximum of 200 days, dropping to 100 days in 2027 and 47 days by 2029. Manual renewal was always a risk; at that cadence, it becomes a job nobody will reliably remember to do. If your certificate isn't renewing automatically, sort that out before it sorts you out — an expired certificate throws a full-screen browser warning at every single visitor.

Beyond the certificate itself, an audit should pick up mixed content (secure pages pulling in insecure assets), missing security headers, and the tell-tale signs of a compromised site: injected pages you didn't create, cloaked redirects sending search traffic somewhere it shouldn't go, and unexplained pages appearing in your index.

Structured Data

Google can read your headings and paragraphs, but it can't easily work out the context — that this string of numbers is a price, that this date is an event, that this business is you. Structured data is how you tell it explicitly.

It earns its keep in two ways now. It's still how you qualify for rich results in Google, and it's increasingly how AI systems extract reliable facts about your organisation rather than inferring them from prose. Clear, accurate markup makes you easier to summarise correctly.

The types worth auditing for most businesses are Organization, LocalBusiness, Article, Product and BreadcrumbList. Validate what you've got with the Rich Results Test or Schema Markup Validator, and while you're in there, clear out anything that's stopped earning its place — plenty of sites still carry FAQ and HowTo markup for rich results Google no longer shows.

Error Management

Much of what we've covered comes down to this: the purpose of an audit is a healthy website. Find and fix your 404s, broken links, redirect chains, soft 404s (pages returning a success code while displaying nothing useful), and any hosting problems, and you're presenting the best possible content to search engines and the best possible experience to users.

Every error chips away at how someone sees your brand. It makes your business harder to deal with, and at worst it derails a would-be customer entirely. Broken links drag on your rankings too, so the cost lands twice. Run a tight ship, audit regularly, and catch the errors before they catch you out.

Tools to Conduct a Technical SEO Audit

You don't need all of these, and you certainly don't need to pay for most of them. Here's what does what, so you can pick the ones that suit the job in front of you.

Where to Start (Free Stuff)

Google Search Console is essential. It's the only tool that tells you how Google actually sees your site rather than how a third party guesses it does. The Pages report shows you what's indexed and, more usefully, what isn't and why. Crawl Stats shows you what Googlebot has been up to. Core Web Vitals gives you field data from real visitors. If you audit with nothing else, audit with this.

Bing Webmaster Tools is the one everyone forgets. It's free, it takes ten minutes to set up, and it gives you a second opinion on crawling and indexing from an engine that isn't Google. Given how much AI-assisted search draws on Bing's index, it's worth more attention than it used to get.

Crawling Your Site

Screaming Frog remains the workhorse. It runs on your machine, crawls up to 500 URLs free, and the paid licence lifts that limit and unlocks the useful extras — JavaScript rendering, Core Web Vitals via the PageSpeed API, custom extraction. It's the tool most of the industry reaches for first, ours included.

Sitebulb does much the same job with considerably more hand-holding. Where Screaming Frog hands you a spreadsheet and trusts you to know what to do with it, Sitebulb explains why each issue matters and prioritises accordingly. If you're auditing without a technical background, this is the friendlier entry point.

Ahrefs and Semrush both run cloud-based site audits on a schedule, which is the real advantage — you get a health score tracked over time rather than a snapshot you have to remember to take. Ahrefs Webmaster Tools gives you a limited version for free for sites you've verified.

Speed and Performance

PageSpeed Insights for both lab and field data on a single URL. GTmetrix for a second read and a helpful waterfall view of what's loading when. Lighthouse, built into Chrome DevTools, for testing pages behind a login or on a staging site the public tools can't reach.

Checking what the bots actually see

No new software needed for this one. Open Chrome DevTools, disable JavaScript, reload the page, and see what's left. If your content vanishes, you've learned something important. The URL Inspection tool in Search Console does the Google-specific version, showing you the rendered HTML it ended up with.

Structured Data

Rich Results Test tells you whether Google can use your markup for enhanced results. Schema Markup Validator validates against the schema.org spec more broadly, which catches things Google's tool ignores because it doesn't happen to use them.

Security

SSL Server Test for a thorough read on your certificate and configuration. Security Headers for a quick grade on what your server is and isn't sending. Both free, both about thirty seconds' work.

Log Files

Everything above tells you what could happen. Your server logs tell you what actually did — which bots came, what they requested, what they got back, and how much of your site they never bothered with. Ask your host or developer for access, then run them through the Screaming Frog Log File Analyser or similar. This is where you find out that Googlebot has been spending its time on your faceted search parameters instead of your service pages.

AI Visibility

The newest category, and the one changing fastest. Tools like Ahrefs Brand Radar and Semrush's AI visibility reporting track whether you're being mentioned and cited in AI-generated answers, and which sources get cited instead of you. Treat the numbers as directional rather than precise — the underlying platforms are moving targets — but the competitive picture is genuinely useful.

How to Do a Technical SEO Audit

So, we've covered the key areas your audit should look at and the tools you'll want open while you do it. But how do you actually work through one? Here's the process, in the order we run it.

1. Prepare

Get your tools open and log in to your CMS. If you're auditing a staging site that's set not to be indexed, update your robots settings so your crawler can reach it — and put the site behind a username and password while you're at it, so your audit tool gets in, but search engines don't. If your site runs a cache layer, warm it first, or your load times will be misleadingly grim.

Decide now what you're measuring against. If you can, note your current index coverage, Core Web Vitals, and organic traffic before you start changing things. It's the only way you'll know afterwards whether any of it worked.

2. Crawl Your Site

Run Screaming Frog, Sitebulb or Ahrefs Site Audit across the site. Add a Google API key to your project settings and most crawlers will pull Core Web Vitals for each page they find, which saves you a job later.

If it's a live site, cross-reference against Google Search Console — the Pages report tells you what Google has actually indexed and why it's excluded the rest, which no third-party crawler can tell you. Check Bing Webmaster Tools too while you're there.

3. Check What the Bots Can See

Take your most important pages — home page, top service pages, best-performing articles — and view them with JavaScript disabled in Chrome DevTools. If the content disappears, you've found something that matters, particularly for AI visibility.

Then check who's allowed in. Look at your robots.txt for directives affecting GPTBot, ClaudeBot, PerplexityBot, Google-Extended and CCBot, and check whether your firewall or CDN is blocking them independently of that. You may well find you're blocking crawlers nobody consciously decided to block.

4. Prioritise

Your crawl report will hand you hundreds of issues, graded by whatever severity scale the tool happens to use. Resist the urge to work down the list in order.

Sort by what's actually costing you: anything preventing indexation comes first, because a page that isn't indexed can't do anything at all. Then problems on your commercially important pages. Then site-wide issues affecting hundreds of URLs, where one fix does a lot of work. A broken link on a 2019 blog post nobody reads is a genuine issue and still not worth a developer's afternoon.

This is the step that separates a useful audit from a long list. It's also the one where a second opinion tends to pay for itself.

5. Evaluate Speed & Performance

If your crawl report didn't cover page speed, run your priority pages through PageSpeed Insights. Remember the two data types: field data only appears for live sites with enough real traffic to generate it, so on a new or quiet site you'll be working from lab data alone. That's fine for spotting obvious problems, but less reliable as a verdict.

6. Assess Mobile and Security

Check content parity first — compare what appears on mobile against desktop on your key pages, because anything that only exists on desktop effectively doesn't exist. Then check tap targets, interstitials, and anything that behaves oddly at narrow widths.

On security, run SSL Server Test and Security Headers. Confirm your certificate renews automatically rather than by someone's diary reminder — with lifespans dropping to 200 days this year and shorter after that, manual renewal is a failure waiting for a quiet week. If you run e-commerce or accounts, check that login-protected pages are genuinely protected and that checkout and account URLs aren't sitting in the index.

7. Review Structured Data and Content Consistency

Validate your schema markup with the Rich Results Test, or the Ahrefs SEO toolbar if you want to inspect pages as you browse. Check the types you actually need are present and correct, and strip out anything that's no longer earning its place.

Your crawl report will also flag duplicate content, missing or duplicated metadata, and pages competing for the same keyword. That last one is more on-page than technical, but it's found during a technical audit — pass it to whoever owns the content.

8. Clean Errors & Redirects

Work through your 404s, inaccessible pages, and redirect problems: chains, loops, and old URLs still being linked to internally. If you've migrated or redesigned recently, spend proper time here — this is usually where lost traffic went.

9. Set Up Monitoring

An audit is a snapshot. Set up alerts so you hear about broken pages and expiring certificates without having to go looking, and put the next audit in the diary. For more on keeping on top of it between times, we've written about tools and tips for easy website management.

Common Technical SEO Issues (And How to Fix Them)

Poor Crawlability or Indexing Issues

• Lack of an XML sitemap file. Typically, your CMS will generate a sitemap for you, or you can create one manually.
• Lack of internal linking. Do a content audit to review and update, or redirect orphan pages.
• Incorrect robots file or robots settings for particular URLs. Check that your /robots.txt file is not set to block anything you want indexed. Robots can also be set as a meta tag on each page, in a response header served by the web server, or in your CMS, so if any robot restrictions are found, there may be more than one place to look.

Duplicate Content or Improper Canonical Tags

• Core content shared across different URLs isn't doing you any favours. Collate and streamline content onto the same URL
• Remove any duplication of content, especially where it has been replicated in whole or in part to target specific keywords - Google can see straight through this shameless strategy!
• Incorrectly setting canonical on listing and faceted search pages — the canonical should be your ‘view all’ URL, and your faceted/paginated URLs should reference that as the canonical.
• Incorrect markup for multi-language sites can cause much confusion. This is a technical fix or CMS configuration, so talk to your developer.

Lack of Mobile Optimisation or Responsive Design 

• Not using responsive images or lazy loading.  This is a website build issue, so ask your developer to update images and set up lazy loading.
• Poor mobile responsiveness can only be resolved by developing a mobile website with responsive layouts.
• Loading video automatically, instead use a poster image that gets replaced with the playing video on click.

Slow-Loading Pages and Poor Core Web Vitals Scores

• A poorly-built website that is slow to query the CMS for content. I’ll admit, there isn’t a quick fix here, as there is a wide range of contributing factors. As a first step, get some technical expertise to assess whether your site has been built in an efficient way that scales for performance (ideally using cached content to avoid having to build the page with database content on each hit).
• Lack of caching, use static page caching and a global CDN like Cloudflare, store images and other assets on a CDN.
• Layouts that move around as they load. Instead, use placeholder content until the desired media has loaded.

Why you should conduct a Technical SEO audit

Your site is online to be seen, so don’t let it fall back into the shadows of the web. Technical SEO audits are your means of keeping tabs on your website’s performance and maintaining its visibility, effectively giving Google a nudge to keep looking your way. 

Regular auditing enables you to be proactive about resolving issues, issues that may be preventing your site from climbing up the SEO rankings. Plus, reports with clear errors and actions also help promote cross-team collaboration towards site maintenance, and who doesn’t love a good bit of teamwork?

…can we help you?

We understand that even with a basic understanding of website auditing, having the resources to conduct one means that this key site maintenance task can be shelved for that ever-elusive lull in work, the one that must be around the corner…?

We’re experts in conducting technical audits of websites at every stage of their lifecycle. If you’ve got some concerns about your website’s performance or search visibility, contact the development team at Mud to get a clearer picture of just how your website looks from a user and Google's point of view.